1. Field of the Invention
This invention relates to a recording device of the ink jet type in which liquid recording medium, generally called ink, is ejected and spattered in the form of droplets from a fine orifice and deposited onto a recording surface. More particularly, the invention is concerned with a recording device of the ink jet type based on ink ejecting principle utilizing heat energy which has not been seen as yet.
2. Description of the Prior Arts
So-called non-impact recording methods have recently drawn public attention because unconfortable noises hardly generate during the recording operation. Among these methods the so-called ink jet recording method is recognized to be particularly important which allows high speed recording on a plain paper without particular image-fixing treatment. Various types of the ink jet recording methods have been proposed, including those already commercialized and others still under development for practical use.
In the ink jet recording method, the recording is effected in such a manner that the liquid recording medium (called "ink" in connection with the explanation of this invention) is ejected and spattered in the form of droplets and further caused to adhere to a recording member such as paper and the like. Such particular recording method is generally classified into two types thereof. One of the two types is the so-called continuous type wherein fine droplets of ink are continuously ejected and spattered, and among them only ink droplets required to effect the recording are selectively introduced and deposited to a recording surface so that the recording is carried out. The other is the so-called ink on-demand type in which only when necessary for the recording, the ink is ejected toward a recording surface in the form of droplets and deposited thereto so that the recording is completed.
The ink on-demand type recording method is advantageous as compared with the continuous type one in that the apparatus for conducting the former can be made simple. That is, the former type does not need many attachments as required for the latter type, such as an ink charger and a deflection controlling mechanism for selecting and introducing the ink droplets necessary for the recording and a collector for ink droplets unnecessary for the recording. Therefore, the apparatus for conducting the former type can be simplified in structure and minimized in size.
In the ink on-demand type ink jet recording method, the ink jet head used therein is formed with a structure, in which the volume of a liquid chamber for storing the ink is varied periodically by mechanical vibration of a piezo vibrating element and the pressure action generated by the variation in the volume of the liquid chamber allows the ejection of the ink in the form of droplets from a discharge orifice. The concrete structure of the recording device is disclosed in, for example U.S. Pat. No. 3,747,120; IEEE Transactions on Industry Applications, vol. IA-13, No. 1, January/February, 1977 and the like. According to such ink on-demand type, the ink droplets are discharged and spattered, on demand, from a discharge orifice, and therefore since it is not necessary to control the course of the discharged ink droplets, the structure of the system can be made extremely simple as a whole.
However, the recording head used in the ink on-demand type recording method is considerably complicated in its inside structure because the ink droplets are formed on the basis of the mechanical vibration of the piezo vibrating element. Further, such recording head inadvantageously requires technique of high level in manufacturing and processing it, and it is considerably difficult to manufacture the recording head with the desired working accuracy. In addition to those drawbacks, the recording device of the ink on-demand type is accompanied by technical difficulty in attaining a multi-array of the recording head portions because the piezo vibrating element is technically difficult to delicately manufacture and mount and also because a small size of the piezo vibrating element having a desired frequency is extremely difficult to obtain, and hence such recording device is inadequate for high speed recording.
As explained in the foregoing, the conventional recording device of ink on-demand type involves fundamental problems to be resolved in respects of the structure, manufacturing the device, applicability to the high speed recording, multi-array of the recording head portions, construction of the system as a whole, and the like.